Palynofacies analysis of the JOG16N-8 borehole, K5 formation from the Maniamba Basin (middle Permian), Mozambique: A contribution for hydrocarbon exploration

Abstract

The Maniamba Basin in Mozambique is surveyed mainly in regard to coal exploration. However, this basin is also known for containing well preserved fossil plants and vertebrate fossils that shed light to the understanding of Gondwana ecosystems. Nevertheless, organic matter analysis (palynofacies) and its implication for depositional environment and hydrocarbon source rock have not yet been performed. Here, we report for the first time in the Maniamba Basin, results from palynofacies analysis combined with thermal maturation and kerogen typification. Palynofacies analysis was applied on 69 samples from the sediments of the JOGN16N-8 borehole, K5 Formation (middle Permian).The results indicate that sediments are dominated by phytoclasts with less abundant sporomorphs and sparse amorphous organic matter (AOM). Three palynofacies were identified suggesting depositional settings in a general proximal and oxic lacustrine-fluvial deltaic environment. The dominance of opaque phytoclasts may be due to wildfires, oxidation conditions before or post deposition in proximity to terrestrial settings and an environment under obliquity cycle controlled monsoon climate. The organic matter composition combined with Spore Colour Index (SCI), pointed out the existence of an abundant type IV kerogen followed by type III in immature phase suggesting very little or no potential for gas exploration. Very few horizons suggest the existence of kerogen type II. This study, gives significant information for better understanding of the variation of organic matter, palaeoenvironment and source rock potential of the studied area.